1. Field of the Invention
The invention relates to a chemical mechanical polishing (CMP) device, and more particularly, to a CMP device comprising at least one nozzle arranged around a base of the CMP device, so as to spray DI water to at least one orifice of a slurry supplier, and thereby prevent the orifice from being clogged.
2. Description of the Prior Art
Elements of wafers are becoming smaller and more integrated, and the requirement for improvement in the depth of focus of lithography is growing. As a result, in very large-scale integration (VLSI) and ultra large-scale integration (ULSI), a plurality of layers of metal interconnects and low K dielectric materials are widely adopted to connect elements of a semiconductor wafer, so as to form high-density circuits. However, these elements result in severe topography of the semiconductor wafer, and thus make a deposition or pattern transfer process become difficult. Therefore, a planarization process has to be performed on the wafer surface before further processing.
Conventional planarization mostly counts on spin in glass (SOG) and resist etch back (REB) processes. However, in processes with a feature size smaller than 25 μm, global planarization can not be reached by using SOG or REB. Therefore, a chemical mechanical polishing (CMP) which can be applied in small feature size processes is adopted in VLSI and ULSI for planarization. Generally, if all parameters are appropriate, planarity can reach up to 94%.
In a CMP process, slurry is provided on a surface subjected to planarization, and a mechanical polishing process is performed on the surface. A conventional CMP device includes a polishing pad, a movable wafer carrier above the polishing pad, and a supplier that supplies slurry and DI water. In the conventional CMP process, the wafer carrier holds a wafer and offers the wafer to the surface of the polishing pad to make them contact. Then, the supplier supplies slurry to the polishing pad through orifices, while the wafer and the polishing pad are in contact and rubbing against each other.
The CMP slurry includes chemical agents and abrasives. The chemical agents can be pH buffers, oxidants, surfactants or the like, and the abrasives can be silica, alumina, zirconium oxide, or the like. The chemical reactions evoked by the chemical agents and the abrasion between the wafer and the polishing pad can planarize the surface of the wafer.
However, slurry and pieces that have come off the wafer during polishing can be left on the device elements thereby contaminating the wafer. For example, particles left can lead to breakdown of oxides, and pieces of polysilicon and metals may cause electric leakage and therefore may decrease the yield and reliability of the wafer. As a result, after the CMP process, a cleaning process needs to be performed to prevent such contamination. The conventional cleaning methods include a wet cleaning process using a chemical basin, a megasonic (ultrasonic, supersonic, or finesonic) cleaning process, and a cleaning process using a brush scrubber. These cleaning processes are able to remove contaminants from the wafer, so as to prevent defects formed on the wafer.
However, such cleaning methods are not able to remove contaminants on the device elements, such as slurry supplier and the polishing head, effectively. For example, the orifices of the slurry supplier may be clogged with crystals of the slurry. In addition, if the crystals fall on the wafer, scratches may be formed on the wafer. Therefore, an effective method needs to be provided to solve this problem.